Quiet operating condition responsive snap switch mechanism

ABSTRACT

A condition responsive snap switch mechanism includes a pair of contacts and a pivoted contact operator for operating the contacts. Spaced-apart fixed stops are provided for limiting movement of the operator. A thin, flexible damping arm is firmly connected to the contact operator and extends between the stops for yieldingly engaging one of the stops upon operation of the contacts.

United States Patent 1 3,629,769

[72] inventor John L.Slonneger [56] ReferencesCited Morris, UNITED STATES PATENTS g g- 337 2,009,410 7/1935 Pearce etal. zoo/1661i [45] Patented 5 2,234,740 3/1941- Pearce ZOO/166R 3,354,280 11/1967 Slonneger 337/326X [73] Assignee General Electric Company Primary Examiner- Bernard A. Gilheany Assistant Examiner-F. E. Bell Attorneys-John M. Stoudt, Radford M. Reams, Ralph E.

Krisher, Frank L. Neuhauser and Oscar B. \Vaddell [54] QUIET OPERATING CONDITION RESPONSIVE gg M E ABSTRACT: A condition responsive snap switch mechanism rawmg includes a pair of contacts and a pivoted contact operator for [52] 0.8. CI 337/318, operating the contacts. Spaced-apart fixed stops are provided 200/166 H for limiting movement of the operator. A thin, flexible damp- [51] int. Cl ..H0lh 37/36 ing arm is firmly connected to the contact operator and ex- [50] Field of Search 200/166 H; tends between the stops for yieldingly engaging one of the 337/318, 133, 319, 326, 321, 322, 317 stops upon operation of the contacts.

PATENTEU m2! sen SHEET 1 UF 2 INVENTOR. 20 John L. Slonneger',

Attorney.

PATENTED nice! nan 31529769 SHEET 2 UF 2 7 e9 INVENTOR. 4 John L.Slonneger,

A 17 borne-y.

BACKGROUND OF THE INVENTION This invention relates to an improved condition responsive snap switch mechanism such as a thermostat unit for use with heating or cooling apparatus.

Many conventional thermostats for heating or cooling applications incorporate a temperature responsive mechanism which acts through a contact operator to operate, that is open and close with snap action, at least a pair of contacts for controlling the heating or cooling apparatus. Such thermostatic elements quite often have low levels of power and overcenter spring arrangements are incorporated in the switch mechanism so that the contact operator and contacts move with a snap action of relatively high velocity and kinetic energy. Normally the operator engages a fixed stop, quite often in the form of an abutment in the switch housing, to stop this movement after the contacts have open or closed. Such engagements or collisions quickly absorb the excess energy of the system; however, they cause unwanted noise. Such noise can be annoying and may, in fact, make the user believe the switch is malfunctioning. This is particularly true for thermostatic switches which are in confined places such as those used with automobile air conditioners, household room thermostats which may be employed in a bedroom and household refrigerators and air conditioners.

SUMMARY OF THE INVENTION Accordingly it is an object of this invention to provide an improved condition responsive snap switch mechanism.

Another object of this invention is to provide an improved condition responsive snap switch mechanism which minimizes the noise of operation and, at the same time, provides reliable switching at the predetermined conditions.

Still another object of this invention is to provide such an improved snap switch mechanism which is simple in construction and operation.

In carrying out the invention, in one form thereof, I provide a condition responsive snap switch mechanism including a housing with a pair of contacts mounted in the housing and a contact operator pivoted on the housing for operating the pair of contacts. The housing includes integrally formed fixed stops to limit movement of the contact operator. There is also provided an external temperature responsive means carried by the housing for actuating the contact operator between the stops and toggle spring means engaging the contact operator for imparting snap action to the operator. A thin flexible damping arm is connected to the contact operator and extends between the stops for yieldingly engaging the stops to minimize impact noise when the snap acting operator is decelerated upon opening and closing of the contacts by the operator.

BRIEF DESCRIPTION OF THE DRAWINGS The above mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be better understood by reference to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view of an improved condition responsive electric switch mechanism embodying my invention in one form thereof;

FIG. 2 is an enlarged side elevational view, partially in section and partially broken away, of the switch of FIG. 1;

FIG. 3 is a'sectional view taken along line 3-3 in FIG, 2;

FIG. 4 is an enlarged perspective view of the contact operator of the switch mechanism of FIG. 1;

FIG. 5 is a somewhat schematic, enlarged partial side elevational view similar to FIG. 2, showing one position of certain operational parts of the switch mechanism;

FIG. 6 is a view similar to FIG. 5, but showing the parts in another position;

FIG. 7 is a view similar to FIG. 5, but showing the parts in still another position; and

FIG. 8 is a view similar to FIG. 5, but showing the parts in yet another position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now particularly to FIGS. 1-3 there is shown a condition or temperature responsive snap switch mechanism 10 which embodies one form of the present invention and is often referred to as cold control." The exemplification switch 10 is an improvement in the general type of temperature responsive switch shown in US. Pat. Nos. 3,065,323, issued to Charles Grimshaw on Nov. 20, I962; 3,065,320, issued to Richard W. Cobean on Nov. 20, I962; and 3,096,4 l9, issued to Louis J. Howell on July 2, I963; all of which are assigned to General Electric Company, assignee of the present invention. Various aspects of such switch mechanisms are shown in detail therein.

Switch mechanism 10 includes a housing 11 which, for example, may be formed by a base 12 of molded phenolic thermosetting plastic, and a U-shaped frame 13, which is formed from a suitable material such as stainless steel. The frame is secured to the base 12 by some suitable means such as posts 14, which extend outwardly from each side of the base and are securely received in mating openings 15 in the frame 13. The frame 13 supports a bellows assembly 16 and a cover assembly 17, which includes means for mounting the switch mechanism upon a suitable supporting panel.

As best seen in FIGS. 2 and 3, the base 12 forms a suitable enclosure for mounting a pair of contacts and their associated terminals. For instance, base 12 serves as a mounting for terminals 18 and 19, the inner portions of which are contained in a cavity 20 of a base. The terminals l8, 19 are securely fastened to the base so as to provide stable external connections for associated wiring and a stable support for a pair of contacts 21 and 22. Contact 21 is a stationary contact, having a contact element 23 electrically and'mechanically connected to terminal 18 by means of a stiff support arm 24. The support arm 24 is riveted to the base 12 for additional strength and rigidity. The movable contact 22 includes a contact element 25 which is electrically and mechanically connected to terminal 19 by a resilient spring arm 26. The spring arm 26 biases the contact element 25 toward the contact element 23 so that the contacts 21, 22 are biased to a closed position. The base 12, frame 13, bellows assembly 16 and cover assembly 17 are securely joined together to form the outer covering of the switch mechanism 10 for mounting and protecting the various operative elements such as the pair of contacts 21, 22. To this end the posts 14 are received in the mating openings 15, the frame 13 is formed with tabs 27 which are bent over the cover 17 and base 12. Other details of one manner of assembling these components may be had by reference to the aforementioned US. Pat. No. 3,065,323Grimshaw and will not be described in further detail here.

Referring now particularly to FIGS. 2 and 3, in order to operate the pair of contacts 21, 22 there is provided a contact operator 28 which includes a base portion 29 with a contact operating arm 30 secured thereto by some suitable means such as rivet 31 so as to extend into the cavity 20. The right end of the base portion (as seen in FIG. 4) is provided with a knife edge 32 which engages one end of a snap action toggle spring 33. The other end of the toggle spring 33 is supported by a movable pivot member 34; the pivot is slidably supported in a pair of channels, such as that indicated at 35, in the base 12. The movable pivot member is longitudinally moved within the base 12 by a differential adjusting screw 36 which is threadily received in the base 12. This provides an adjustable support for the right side of the toggle spring 39 so that, by adjusting the position of the screw 36, the tension of the toggle spring 39 may be adjusted. The operator 28 is also supported by means of a pair of shoulders 37 which extend outwardly from each side of the base portion 29 and are received in cooperating slots 38 formed in the U-shaped frame 13 (see FIG. 1). Thus the contact operator 28 is mounted for pivotal movement about the engagement of the shoulders 37 with the slots 38, with the toggle spring 33 biasing the operator for movement with a snap action.

The base portion 29, is also provided with a pair of laterally disposed channels 39 which are positioned slightly toward the knife edge 32 from the shoulders 37. The channels 39 provide arcuate pivots for supporting a bearing 40. The bearing 40 includes upper shoulders 41 which fit upon channels 39 and depending, parallel pairs of struts 42. At their other ends, struts 42 support a cuplike base 43. The channels 39, being positioned between the knife edge 32 and the pivot points of the shoulders 37, may be used for providing a force on the contact operator 28 tending to rotate the operator in a clockwise direction (as seen in FIG. 2). To this end a range spring 44 engages, at its lower end, a nut 45in which is threaded an adjusting screw 46. The lower portion of the screw 46 is provided with a shoulder 47 which engages the base 43 of the bearing 40. Also the lower end 48 of the screw extends through the base 43 and is received in a cup 49 of bellows 50. The range spring 44, acting through the nut 45 and screw 46, exerts a continuing force on the bearing 40 tending to rotate the operator 28 in a clockwise direction (as seen in FIG. 2).

This force may be overcome by increasing the force which the bellows 50 exerts on the lower end 48 of the screw 46, which tends to lift the screw 46 and bearing 45 against the force of the range spring 44. The increase and decrease of the force of the bellows 50 is utilized to provide a cumulative force responsive to a .condition external to the switch mechanism, such as a sensed temperature for instance. To this end the bellows is connected to a bulb 51 by means of capillary tube 52. The bellows, bulb and capillary tube contain a charge of suitable vapor such as, for instance, dichlorodifluoromethane, butane, methyl chloride. As the temperature of the bulb rises or falls, the pressure of the vapor charge increases or decreases. This causes a corresponding increase or decrease in the force exerted on screw end 48 by the bellows 50, all in a well-known manner. Thus, the pivotal movement of the operator 28 is responsive to the condition external to the switch and, in the cold control of the exemplification, it is responsible to a temperature sensed by the bulb 51. Assuming the operator 28 is between the positions shown in FIGS. and 6, a decrease in the force exerted by bellows 50 will cause the operator to creep to the position shown in FIG. 6. The operator will then snap from the position of FIG. 6 and come to rest approximately halfway between the positions shown in FIGS. 7 and 8, after vibrating between these last two positions. Thereafter, an increase in the force exerted by bellows 50 will cause the operator to creep to the position shown in FIG. 7 and then snap and ultimately come to rest approximately halfway between the positions shown in FIGS. 5 and 6, after vibrating between these last two positions.

By varying the compression of the range spring 44 the sensed temperature level at which the cold control operates may be adjusted. To this end there is provided a manually adjustable cam 53 which is rotatably supported on cover assembly 17 by a short rotatable shaft in the form of stud or rivet 54, the other end of which is connected to a rotatable plate 55. An operating arm 56 extends generally radially outwardly from the plate 55 so that rotation of the arm 56 causes the plate 55, stud 54 and cam 53 to also rotate. A spring washer 57 is captured between the cover assembly 17 and the plate 55 to retain the assembly of the plate 55 and cam 53 in a preset angular position. The cam 53 engages one end 58 ofa cam follower 59 which is pivotally mounted on the U-shaped frame 13. The upper edge of the range spring 44 engages the underside of the cam follower 59 so that, as the cam follower responds to the rotary positioning of the cam, the amount of compression of the range spring 44 between the cam follower 59 and the nut 45 is changed. Also suitable openings such as that shown at 60 may be provided in the cover assembly 17 and plate 55 for insertion of a screwdriver or other tool to calibrate the mechanism by adjusting the screw 46.

As thus far described the collective force exerted on the contact operator 28 by the bellows 50, the range spring 44 and the toggle spring 33 will cause the operator to snap in clockwise and counterclockwise directions respectively in response to the bellows sensing two different predetermined temperatures. The particular temperature at which the bellows will allow the range spring to overcome the toggle spring is determined by the setting of the cam 53 while the differential adjusting screw 36 is used to set the differential of the mechanism, that is the difference between the sensed temperature at which the operator will snap in one direction and the sensed temperature that it will snap in the other direction.

The operating arm 30 of the contact operator 28 is formed to cooperate with the contacts 21, 22 to effect a snap action opening and closing of the contacts in a predetermined manner as the operator pivots in its two directions. To this end the operating arm 30 extends into the chamber 20 and overlies the spring arm 26 so that, as the operator 28 snaps in a clockwise direction (as seen in FIG. 2), the operating arm 30 will engage the arm 26 and move it downwardly to open the contacts. As the contact operator snaps back in the counterclockwise direction, the operating arm 30 will move away from the spring arm 26 and allow the contacts to reclose.

The snap action provided is necessary for assuring proper operation of the contacts. However, in many prior art condition responsive switches it has resulted in the contact operator 28 coming into contact with some portion of the housing with considerable force at the end of each of its strokes, that is both at the end of its counterclockwise and its clockwise movement. Such high impact engagements generate noise which, in many instances, is objectionable. Referring now to FIGS. 2-4 it will be seen that, in accordance with one form of the present invention there is provided a flexible damping arm 61 which, in the exemplification, is formed from a pair of parallel, juxtaposed leaf spring elements 62 and 63. In the exemplification the leaf springs 62 and 63 are sandwiched between the contact operator 28 and a backing member 64 and firmly held in place by a means of a rivet 65 which extends through the entire assembly. The operator 28 is formed with an extension 66 which extends outwardly adjacent the leaf spring 63 to a point beyond the edge of the backing member 64. Both the backing member 64 and the extension 66 are smoothly curved away from the damping arm 62.

Referring particularly to FIG. 2 it will be'seen that the damping arm 61 formed by the leaf spring 62, 63 extends into a gap 67 formed between a pair of spaced apart stops 68 and 69. The stops 68 and 69 are formed integrally with the housing and, in the exemplification, are formed as part of the one channel 35 in the base 12. As the operator 28 snaps in a clockwise or counterclockwise direction for operating the contacts 21, 22, and after the contacts have been either opened or closed, the damping arm 61 engages the corresponding stop so as to limit the pivotal movement of the operator and slowly absorb the energy of the snap action until the vibrating operator comes to rest. As the damping arm engages the stop it will flex so that the noise previously attendant to quickly stopping the operator is greatly reduced to a level which is acceptable.

The smoothly divergent curving of the extension 66 of the operator 28 and the backing member 64 enables the damping arm to flex smoothly about the curved portions of these members. This allows the absorption of the energy to occur in a shorter overstroke and also prevents the damping arm becoming permanently set in a flexed configuration. The damping arm 61 of the exemplification is shown as being composed of two leaf spring elements 62 and 63 which may be some suitable material such as heat treated stainless steel or beryllium these elements absorbs some of the energy. Also, as best seen in FIGS. 5-8, the leaf spring member 63 is formed at its end with a portion 70 which is bent or stepped away from the corresponding end of the leaf spring 62. This enables the amount of travel of the contact operator 28 to be adjusted, that is, the further the end 70 is stepped away from the leaf spring 62 the less the operator will travel from engagement of the damping arm with one stop to engagement of the damping arm to the other stop.

FIGS. 5-8 illustrate the relative positions of the parts as the contact operator 28 moves from one extreme position with the contacts 21, 22 closed (as seen in FIG. 5) to the other extreme position with the contacts fully opened (as seen in FIG. 8). The damping arm 61 engages each stop after the contacts have been either opened or closed respectively so as to limit movement of the operator under normal operating conditions. When the switch mechanism is properly calibrated, the damping arm 61 will ultimately stop the pivotal movement of the operator approximately halfway between the positions shown in FIGS. 7 and 8, when snapping from the position shown in FIG. 6 to open the contacts, and will ultimately stop the pivotal movement of the operator approximately halfway between the positions shown in FIGS. 5 and 6, when snapping from the position shown in FIG. 7 to close the contacts. The noise resulting from the damping arm striking the stops is considerably less than the noise if the snap action movement were stopped by the operator striking the stops.

One purpose of having the extension 66 of the contact operator project beyond the backing member 64 is illustrated and may be seen by viewing FIG. 8. If the contact operator were to rotate much further in a clockwise direction than that shown in FIG. 8, the extension 66 would snugly compress the damping arm 61 against the slanted portion 71 of the stop 69 so as to positively limit any further clockwise movement of the operator without overstressing the damping arm. This is a benefit particularly during the manufacturing process. When the switch mechanism is properly calibrated the damping arm 61 will stop pivotal movement of the operator 28 without any overstressing of the damping arm; however, in the course of manufacture, as the switch mechanism is assembled and first calibrated, the contact operator 28 may be caused to go in one direction or the other an excessive amount. This could overly stress the damping arm. Thus the extension 66 is provided so that it projects beyond the backing member 64 and into interfering relationship with the slanted portion 71 of the stop 69. The manufacturing process is controlled so that if there is any excessive movement of the contact operator before calibration it will be in the clockwise direction (as seen in FIGS. 5-8). Thus the extension 66 will firmly engage the damping arm 61 and force it against the slanted portion 71 of stop 69 without excessively flexing the damping arm.

While in accordance with the patent statutes I have described what, at present, is considered to be a preferred embodiment of my invention, it will be obvious to those skilled in the art that numerous changes and modifications may be made therein without departing from the invention, and it is therefore aimed in the appended claims to cover all equivalent variations as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A condition responsive snap switch mechanism, including:

a. at least one set of contacts mounted having open and closed positions;

b. a pivotally mounted contact operator engaging one of said set of contacts for effecting snap action opening and closing of said set of contacts;

c. spaced apart fixed stops for limiting pivotal movement of said operator;

d. a thin, flexible damping arm firmly connected to said operator and extending between said stops for yieldingly engaging said stops upon opening and closing of said set of contacts.

2. A switch mechanism as set forth in claim 1 wherein said damping arm includes at least a juxtaposed pair of flexible leaf members.

3. A switch mechanism as set forth in claim 1 wherein said operator extends adjacent said spring arm into an interfering relationship with one of said stops for positively stopping movement of said operator after predetermined flexure of said damping arm.

4. A switch mechanism as set forth in claim 1 wherein one end of said damping arm is fixed between said operator and a backing member; said operator and backing member being smoothly divergent toward the other end of said damping arm.

5. A condition responsive snap switch mechanism, including:

a. a housing;

b. a pair of contacts mounted on said housing;

c. a contact operator pivoted on said housing for operating said pair of contacts;

d. said housing having integrally formed fixed stops to limit the movement of said contact operator;

e. external temperature responsive means carried by said housing for actuating said contact operator between said stops;

f. toggle spring means engaging said contact operator for imparting snap action to said contact operator;

g. a thin, flexible damping arm connected to said contact operator and extending between said stops for yieldingly engaging said stops upon operation of said pair of contacts by said contact operator.

6. A switch mechanism as set forth in claim 5 wherein said damping arm includes at least a juxtaposed pair of flexible leaf members.

7. A switch mechanism as set forth in claim 5 wherein said operator extends adjacent said spring arm into an interfering relationship with one of said stops for positively stopping movement of said operator after predetermined flexure of said damping arm.

8. A switch mechanism as set forth in claim 5 wherein one end of said damping arm is fixed between said operator and a backing member; said operator and backing member being smoothly divergent toward the other end of said damping arm.

t l 1F 

1. A condition responsive snap switch mechanism, including: a. at least one set of contacts mounted having open and closed positions; b. a pivotally mounted contact operator engaging one of said set of contacts for effecting snap action opening and closing of said set of contacts; c. spaced apart fixed stops for limiting pivotal movement of said operator; d. a thin, flexible damping arm firmly connected to said operator and extending between said stops for yieldingly engaging said stops upon opening and closing of said set of contacts.
 2. A switch mechanism as set forth in claim 1 wherein said damping arm includes at least a juxtaposed pair of flexible leaf members.
 3. A switch mechanism as set forth in claim 1 wherein said operator extends adjacent said spring arm into an interfering relationship with one of said stops for positively stopping movement of said operator after predetermined flexure of said damping arm.
 4. A switch mechanism as set forth in claim 1 wherein one end of said damping arm is fixed between said operator and a backing member; said operator and backing member being smoothly divergent toward the other end of said damping arm.
 5. A condition responsive snap switch mechanism, including: a. a housing; b. a pair of contacts mounted on said housing; c. a contact operator pivoted on said housing for operating said pair of contacts; d. said housing having integrally formed fixed stops to limit the movement of said contact operator; e. external temperature responsive means carried by said housing for actuating said contact operator between said stops; f. toggle spring means engaging said contact operator for imparting snap action to said contact operator; g. a thin, flexible damping arm connected to said contact operator and extending between said stops for yieldingly engaging said stops upon operation of said pair of contacts by said contact operator.
 6. A switch mechanism as set forth in claim 5 wherein said damping arm includes at least a juxtaposed pair of flexible leaf members.
 7. A switch mechanism as set forth in claim 5 wherein said operator extends adjacent said spring arm into an interfering relationship with one of said stops for positively stopping movement of said operator after predetermined flexure of said damping arm.
 8. A switch mechanism as set forth in claim 5 wherein one end of said damping arm is fixed between said operator and a backing member; said operator and backing member being smoothly divergent toward the other end of said damping arm. 